Zeolite can be used to soften water when
Ca2+ or Mg2+ ions in zeolite are replaced by Na+ions in hard water
Ca2+ ions in zeolite are replaced by Mg2+ ions in hard water
Na+ions in zeolite are replaced by Ca2+ and Mg2+ ions in hard water
None of the above
Hard water contains chlorides, sulphates, carbonates and bicarbonates of Ca2+ and Mg2+. When water softening takes place, Ca2+ or Mg2+ ions are replaced by Na+ ions present in zeolite.